Hi!
Boros Attila a écrit :
> Hello Patrice,
>
>
----8<---- SNIP SNIP SNIP -----
> So there is really no silver bullet, and I should consider choosing a
> color space based on what kind of image I'm working with, and what the
> final output will be, and working with ProPhotoRGB in 16 bit is just a
> safe bet. Then the final step will be to convert to sRGB before saving
> for web. Can there be a loss of image detail/color when I perform such
> a conversion?
>
Yep, with ProPhoto RGB/16bit, you're probably quite safe (16 bit is 16
times better and the 12 bits originally in RAW files, so this allows for
a good clearance).
In 8 bit you're definitely not.
> Let's say I have an image which fits perfectly into sRGB.
>
> A.)
> - I use ACR to open the image in Photoshop using ProphotoRGB.
> - Apply levels, curves, sharpening etc.
> - Convert to sRGB then save for web.
>
> B.)
> - I use ACR to ipen the image in Photoshop using sRGB.
> - Apply levels, curves, sharpening etc.
> - No need to convert, this is already sRGB so just save for web.
>
> Assuming that in both cases I work in 16 bits/channel mode will there
> be any differences between A.) and B.)? With other words, can
> colorspace conversions lead to a loss of information? It would seem
> that in B.) there is no color space conversion, it's sRGB all the way,
> but there is a catch: the article says that ProPhotoRGB is Camera
> Raw's native colour space. So if I get this right there will be a
> conversion in both cases.
>
>
I'd say in 16 bit you probably won't see any difference. However, if you
want to do a bit more advanced retouching, then save not only for web,
but for print also, I'd recomment A, so you do the retouching just once
for all.
BTW, in case A, there are two color conversions:
- Camera -> ProPhoto RGB (ACR does this one)
- ProPhotoRGB -> sRGB (before saving, in PS)
In case B, there is just one in ACR for Camera -> sRGB
(I assume here that the RAW camera data is in its own sensor-specific
color space.)
Just like curves/levels adjustments, any color space conversion will in
theory destroy some information, because you relocate some colors to
other values, and with a finite number of values, some colors that were
initialy separate will become identical. My bet is that in 16bits, with
16 times more precision than actually present in the original data, this
is not an issue.
Anyway, if the final result is just for 8bit Web display, we just
shouldn't bother with this, as most web viewers won't have a properly
calibrated screen.
I'd have very different conclusions in 8 bits, though!
> PLG> Just my 2 cents (a bit long, but these are Euro cents).
> Thank you Patrice, it is well worth it:)
>
> --
> Attila
>
>
Best regards
Patrice
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